Forces and Newton's laws of motion

This course is a part of AP®︎ Physics 1, a 12-course Topic series from Khan Academy.

Let's learn about what a force is and how Newton changed the world's view of how reality works.

This course contains 7 segments:

Introduction to forces and free body diagrams

This lesson reviews different types of forces and how to draw free body diagrams to represent the forces on an object.

Newton's first law: Mass and inertia

Newton's first law, also called the law of inertia, says that there must be a net external force on an object for there to be any change in velocity.

Newton's second law

Newton's second law tells us how much an object will accelerate for a given net force.

Newton's third law

Newton's third law says that forces always occur in pairs. For example, if the Earth is pulling down on you, you are also pulling up on the Earth with a force of equal magnitude and opposite direction.

Angled forces

Sometimes forces are applied at an angle. We can use trigonometry to separately analyze the force components along the coordinate axes.

Inclined planes

What forces are acting on you when you slide down a frictionless ramp? In this lesson we'll learn how to analyze the motion of an object on an inclined plane.

Friction

What keeps a parked car from sliding down a slope? This lesson looks at what happens when we include static and kinetic friction forces between two objects.